Coaxial vacuum relay having plural contacts



4, 1965 M. SANTANGELI 3,202,784

GOAXIAL VACUUM RELAY HAVING PLURAL CONTACTS Filed March 15, 1963 United States Patent COAXIAL VACUUM RELAY HAVENG PLURAL CGNTACTS Mario Santangeli, Milamltaly, assignor to International Standard Electric Corporation, New York, N.Y., a

corporation of Delaware Filed Mar. 13, 1963, Ser. No. 264,957 Claims priority, application Italy, Mar. 14, 1962,

Patent 684,714 Claims. (Cl. 200-487) The present invention relates to an improvement in relays for switching electrical circuits and particularly to relays used with coaxial cables carrying VHF currents.

The present invention provides a very simple and economical structure for a relay unit which makes a firm connection between coaxial conductors and does not cause reflections; when inserted in a RF line carrying VHF currents. The characteristics of the present relay are such that negligible power losses permit its use forfrequencics up to and over 500 megacycles. The constructional embodiment thereof is very simple and uses standard series components suitably arranged to obtain a unit of small volume. The electric contacts are enclosed in sealed glass vessels of a known type, as shown for example, in US. Patent Nos. 3,059,074 issued October 1 6, 1962 and 2,957,961 issued October 25, 1960. The contacts are thus completely isolated from the efiects of weather agents containing acids or salts which reduce the conductivity of the contact surfaces. The power for the actuation of this relay is of the order of a few watts and its construction is such that the load may be connected for a long time without damaging the elements. A typical use ior the relay is to switch a radio-antenna from a receiver to a transmitter.

For the-best operation, the features of the relay should be as follows:

(a) A very low contact resistance between contact points at the highest frequency,

(b) Small or absence of wear at the contact points githout change in the surface conductivity when current ows,

(0) Very low electrostatic capacity between the contact carrying members to prevent power leakage-effect in the cable, and

(d) High isolation at open circuit. Prior art relays have had difliculties in obtaining these conditions particularly for use with coaxial connectors.

In the present invention the above characteristics are achieved by use of contacts made of magnetic metal alloys having a high electrical conductivity and which are sealed in an evacuated vessel to form the inner conductor of the coaxial relay arrangement. The electrostatic capacity between the open contacts is not more than two picofiarad, where-as the DC. isolation resistance measured 0n the switching terminals can reach a value of 10 ohm. The remaining leakage power depends upon the quality of the dielectric of the connectors. A non-magnetic metal tube completes the outer concentric conductor for the coaxial connection.

A further feature of the present relay is the ability to adjust the sensitivity of operation by using an additional small permanent movable magnet placed near the terminals abutting the switching elements.

A better understanding of the construction and mode of operation will result from the following description taken in conjunction with the figures of the accompanying drawings illustrating two embodiments of the present invention, given by way of example, in which:

FIG. 1 is a front view of a vacuum coaxial relay of an inverted T type with the bottom portion partially sectioned.

FIG. 2 is a longitudinal section of the relay of FIG. 1.

FIG. 3 is a cross section taken along line A--A of the portion of the relay which includes the switch contact terminations.

FIG. 4 is an alternative embodiment of a relay of the inverted Y type, in a longitudinal section view.

Referring to FIG. 1 there is shown a vacuum coaxial relayin the form of an inverted T; the three ends 1-24; of which are provided with coaxial connectors of a standard type. The central portion is made of an outer concentrically arranged short metal tube supporting an inner sealed switchingunit of the type mentioned above. The inverted T shape is given only by way of example and the relay can similarly be formed as an inverted Y or in other suitable forms.

The metal tube forms the outer conductor of the coaxial unit and is surrounded by an energizing coil 4. FIG. 2 shows the internal construction of the novel vacuum coaxial relay in which a vessel or envelope 6 containing the magnetic contacts at the ends of longitudinal reed type magnetic elements, is positioned along the axis of metal tube '5 of non-magnetic material. The output contacts are selectively connected to the central conductor of a coaxial cable terminating on the input connector 1.

J The internal diameter D of metal tube -5 is such with respect to the external diameter d of the enclosed gl tube 6, that characteristic impedance By using supporting discs 16 of suitable dielectric material, the dielectric constant value 6 can be modified so as to obtain the desired impedance.

These supporting means serve also to center the glass tube containing the internal conductor in the correct axial position with respect .to the metal tube 5. Glass tube 6 is preferably of a standard known clip type device such as shown in the previously cited Patent No. 3,059,074, with one end having only one terminal 7 protruding. This unit is easily replaced in case of failure since it is held in place by only two soldering connections made through opening 10 and can be removed from tube 5 through the top portion thereof alter connector 1 is removed by unscrewing screws 11 from the top of the relay.

FIG. 3 shows a section through the base of the vacuum coaxial relay. The output switching contacts contained in glass tube 6 terminate with two wires 8-9 protruding from the vessel which can be straight or bent to be electrically joined to the central terminal of connectors 2-3 to complete the connections to the coaxial cable conductors of either of two external lines. As an example, connector -2 may be connected to a radio receiver, representing the stationary condition of the relay, and connector 3 connected to a radio-transmitter, representing the operating condition of the relay. The two connectors 23 are secured by screws to non-magnetic metal block 12 which is integral with tube 5. An opening 10 made in the block, centered on the axis of tube 5, facilitates the soldering of the central conductors of two connectors 2-3 to the respective leads 39 of the clip device 6. The opening 10 is closed by a suitable non-magnetic plug.

The vacuum coaxial relay is energized by means of coil 4 surrounding metal tube 5. At the opposite ends of this coil can be disposed two plates of magnetic material (1313') in order to increase the density of the magnetic flux generated by the exciting coil 4 at the opposite ends of the sealed clip device. An external magnetic case 15 completes the magnetic circuit of the plates 13-13 and creates a shield for the coil 4.

To increase the sensitivity of operation of the relay, to permit use of a lower voltage across the coil to close the aeoayzsa 7 make contacts of the relay, a small permanent magnet 17 (FIG. 1) is afiixed to a plug 18 in such a way as to position one of its poles adjacent leads 8-9 of the device 6. The magnetic polarity is suitably selected so that the currentdirection in the coil winding is in an aiding relation with the magnetic flux created by said coil 4. The magnet 17 may be moved toward or away from leads -89 by sliding or screwing plug 18 into opening 10. By this means the required voltage across the ends of coil 4, can, for example, be decreased from 8 v. to 2 v. without changing the coil characteristics for actuating the relay. The ampere-turns of the relay can thus be brought to a minimum by using this polarizing magnet.

FIG. 4 shows another form of relay in place of the inverted T shape. Modifying the angle of the connectors 2-3 with respect to the axis of tube 5 an inverted Y shape is obtained which provides an improved high frequency coupling. The leads 8-9 protruding from vessel 6 will be diverged as shown in FIG. 4 and soldered to the center conductors of connectors 2-3. Suitable lateral openings may be provided for assembly operations Experimental tests were conducted on some units manufactured as described above inserting the relays in circuits of 50 ohm impedance carrying VHF currents at frequencies from 50 to 500 megacycles. No power leakage, and an improvement in the standing wave ratio, as compared to known commercial coaxial relays, were observed. Average connection losses of less than 0.5 db and VSWR less than 1.2 were measured up to 500 megacycles. Long life expectancy is greater than 10 million operations.

While two embodiments of the present invention have been described above by way of example, it is to be clearly understood that other mechanical arrangements and shapes different from those illustrated could be designed and different types of sealed contact switches could be used, without departing from the spirit and the scope of the present invention as set forth in the appended claims.

What is claimed is: V

1. A high frequency coaxial relay switching device comprising a sealed glass Vessel, a magnetically operable switching contact extending within said vessel at one end, a pair of spaced contacts extending within said vessel from the other end and positioned about each side of said switching contact, each said contact having an externally extending conductor portion forming an inner conductor of a coaxial line, a metal tube of non-magnetic material having a first portion positioned concentrically about said vessel and externally extending conductor at said one end to form the outer conductor of one coaxial line, said metal tube having a second and third portion positioned about the external conductors at the other end to form the outer conductors of the other coaxial lines, said vessel and contacts being positioned entirely within said first metal tube portion and an energizing coil surrounding said first portion of said metal tube and vessel to selectively connect said switching contact to one of said pair of contacts.

2. The device of claim 1 including end plates of magnetic material positioned adjacent the ends of said coil and a longitudinal enclosure of magnetic material about said coil to form a magnetic circuit and shield therefor.

3. The device of claim 2 including a permanent magnet adjustably positioned at said other end of said vessel external thereto and entirely within said metal tube adjacent said pair of contacts to control the sensitivity of operation.

4. The device of claim 2 wherein said coaxial lines form a T shaped junction.

5. The device of claim 2 wherein said coaxial lines form a Y shaped junction.

References Cited by the Examiner V UNITED STATES PATENTS 2,264,124 11/ 41 Schreiner 200153 2,845,506 7/58 De Lucia a 20087 2,907,846 10/59 Wilhelm 200-93 2,957,961 10/ Juptner 200-87 3,087,125 4/63 Scholefield 200-87 BERNARD A. GILHEANY, Primary Examiner. ROBERT K. SCHAEFER, Examiner. 

1. A HIGH FREQUENCY COAXIAL RELAY SWITCHING DEVICE COMPRISING A SEALED GLASS VESSEL, A MAWGNETICALLY OPERABLE SWITCHING CONTACT EXTENDING WITHIN SAID VESSEL AT ONE END, A PAIR OF SPACED CONTACTS EXTENDING WITHIN SAID VESSEL FROM THE OTHER END AND POSITIONED ABOUT EACH SIDE OF SAID SWITCHING CONTACT, EACH SAID CONTACT HAVING AN EXTERNALLY EXTENDING CONDUCTOR PORTION FORMING AN INNER CONDUCTOR OF A COAXIAL LINE, A METAL TUBE OF NON-MAGNETIC MATERIAL HAVING A FIRST PORTION POSITIONED CONCENTRICALLY ABOUT SAID VESSEL AND EXTERNALLY EXTENDING CONDUCTOR AT SAID ONE END TO FORM THE OUTER CONDUCTOR OF ONE COAXIAL LINE, SAID METAL TUBE HAVING A SECOND AND THIRD PORTION POSITIONED ABOUT THE EXTERNAL CONDUCTORS AT THE OTHER END TO FORM THE OUTER CONDUCTORS OF THE OTHER COAXIAL LINES, SAID VESSEL AND CONTACTS BEING POSITIONED ENTIRELY WITHIN SAID FIRST METAL TUBE PORTION AND AN ENERGIZING COIL SURROUNDING SAID FIRST PORTION OF SAID METAL TUBE AND VESSEL TO SELECTIVELY CONNECT SAID SWITCHING CONTACT TO ONE OF SAID PAIR OF CONTACTS. 